It has long been desirable to reduce cost of operation, fossil fuel consumption, and emissions of pollutants and greenhouse gases from vehicles such as automobiles, buses, trucks, trains, boats and aircraft powered by internal or external combustion engines (ICE and ECE) and other Prime Movers. Over the last two centuries, many inventions have served to improve the fuel consumption of automobiles and trucks and other powered vehicles and save precious fossil fuels. Examples include high-compression engines, multi-speed and overdrive transmissions, aerodynamics, radial tires, electronic fuel injection, electronic engine and powertrain controls, lighter but stronger materials and improved methods of construction. The introduction and commercialization of hybrid vehicles with the capability to store energy through regenerative braking and reuse the same during acceleration have demonstrated some dramatic improvements in fuel mileage.
The total fuel consumed by a vehicle depends on the distance traveled and the basic vehicle design, but is also significantly dependent on how it is operated. Every passenger car and light truck for sale in the US has a window sticker displaying the estimated mileage (miles per gallon) based on standard “Urban” as well as “Highway” test cycles. Driving behaviors and routes also affect mileage, such as payload, speed, rates of acceleration, transmission gear ratios and shifting, rates of deceleration and braking, upgrades and downgrades, cold and warm starts, zero speed idling, etc. As the automobile EPA mileage sticker states, “Your mileage may vary.”
While the EPA Mileage Sticker provides useful information to buyers and manufacturers of automobiles, owners have frequently complained that they fail to achieve the posted results in “real world” driving. As a result the EPA has twice revised the calculation procedure to reduce both the Urban and Highway numbers. This may mean that drivers often fail to drive in the more fuel-efficient ways, or that the standard EPA Test Procedures are not representative of a typical trip. Consequently there may exist an opportunity to better inform drivers on ways to save fuel.
Since the early days of the automobile, “experts” have given advice to operators on ways to reduce fuel consumption, and often to the experts' chagrin, such advice is mostly ignored. The most oft-repeated advice to save fuel is to drive and accelerate more slowly. This same advice can be seen today on the EPA and other fuel-conscious Websites. This idea led to the National Speed Limit of 55 mph, enacted by Congress in 1974 following the Arab Oil Embargo, and not repealed until the mid-1990s.
Many devices have been marketed to operators of vehicles with the aim or claim to reduce fuel consumption and cost. Some of these devices actually work. One of perhaps the earliest, most simple and inexpensive devices for automobiles is the intake manifold vacuum gauge. Such devices were introduced decades ago and are still available today from the aftermarket. In use, operators are advised to not operate the engine at low manifold vacuum, i.e. large throttle openings, and the instrument had green, yellow, and red ranges.
The next step in technology was a variety of mechanical devices designed to display to the operator an indication of the fuel consumed per distance traveled, in miles per gallon of fuel, or liters per 100 kilometers, or simply mileage. Patent records reveal variations on such devices from the 1920s or earlier to present day.
Developments in emissions regulations, solid-state electronics, microprocessors, and electronic engine controls have provided additional sensors and means of obtaining speed, fuel flow, and other information from vehicles, and means to compute and display information to operators. For example, displays of actual instantaneous miles per gallon (mileage) or liters per 100 kilometer became available factory installed on many vehicles as well as the aftermarket in the form of “trip computers.”
U.S. Pat. No. 3,983,533 to Goszyk et al. used analog electronic devices to produce a MPG display with a warning device. U.S. Pat. No. 4,050,295 to Harvey described a digital electronic measuring system. U.S. Pat. No. 4,287,503 to Sumida provides a “running data central display arrangement for motor vehicles and the like” for abnormal conditions as well as selected running conditions, including “average fuel cost” but fails to define what is meant or how it is calculated. The method and device of Barske in U.S. Pat. No. 4,590,568 determines a rate of fuel consumption and controls the vehicle engine to achieve a desired distance for a given quantity of fuel. U.S. Pat. No. 4,593,357 of Van Ostrand, et al. describes a portable computer based performance monitoring system with an improved fuel flow meter and a display of mileage. U.S. Pat. No. 4,706,083 to Baatz, et al. describes an improved fuel flow meter to determine and display a “performance ratio.”
U.S. Pat. No. 6,411,888 to Weisman, II describes a driving efficiency gauge and display, wherein a measure is derived and displayed by a calculation of losses of braking and idling, and calculating the cost of operating a vehicle per unit distance traveled or per unit of time, and an instantaneous braking velocity cost per unit distance. Although these calculations may have merit to individual drivers and fleet operators, it seems abstract and only measures part of the complete driving cycle.
U.S. Pat. No. 6,694,245 to Kinami et al. describes another method to calculate fuel flow based on the measure of air flow and fuel to air ratio. This information is then used to calculate and display measures such as “excess drive force,” “reserve drive force,” a “hard braking/hard acceleration warning lamp,” and average fuel consumption rate. Histograms are also recorded in the data processor. The fuel flow measure may be valid but seems obvious, and the definition or threshold of “excess drive force,” “hard braking/acceleration,” etc. have to be made by an “expert,” which leads to an arbitrary and capricious measure to an operator.
U.S. Pat. No. 6,975,217 to Endoh describes another vehicle fuel mileage meter which displays the mileage after a vehicle has exceeded a predetermined threshold speed. Such information may make good advertising claims for manufacturers, but neglects a significant part of the real world driving experience.
U.S. Pat. No. 6,988,033 to Lowery et al. describes using the vehicle On-Board Diagnostics (OBD) systems, wireless data transmission, and the Internet to determine a vehicle's fuel efficiency. This document describes another system for obtaining vehicle speed, Mass Air Flow (MAF) and/or percent engine load and other data from the OBD port, calculating fuel flow, sending the data over wireless data and/or cell phone systems to the Internet and a host computer. The host computer is used to determine properties of the vehicle such as tire pressure, status of the fuel injection system, etc. The average fuel mileage and amount of money spent on fuel is calculated and relayed back to the vehicle operator. The system may be of benefit to vehicle manufacturers or fleet operators, but does not seem to merit the complexity of the system to a vehicle owner.
U.S. Pat. No. 6,694,806 to Kumagi et al. describes another method to calculate fuel flow based on engine rotation speed and accelerator depression and looking up BSFC on an engine performance map. This information is then used to compute, display, and record fuel mileage over several different operating conditions of the vehicle, i.e. another mileage meter.
U.S. Pat. No. 7,072,762 to Minami et al. describes another evaluation system for vehicles, summarizing fuel consumed during operations that worsen fuel economy such as acceleration. The document fails to describe how best to accelerate a vehicle without consuming more fuel than required at a steady speed, nor the consequences of different rates of acceleration.
U.S. Pat. No. 7,603,228 to Coughlin describes a “haptic” (sense of touch) device to vibrate the accelerator pedal when an aspect of vehicle operation crosses a speed or acceleration threshold. The patent description indicates that a possible message “could include . . . the money saved per hour like a wage being earned through better driving habits,” but does not describe how this might be carried out. Several higher cost modes of vehicle operation are described and when thresholds are exceeded the vibration is initiated. As with other referenced devices, the thresholds are set by the expert, whoever that might be, using unknown criteria.
Overall, the prior-art devices fail to provide a true sense of the best way to operate the vehicle during all modes normally encountered, and raise unanswered questions. How does one decide if the current mileage is too high or too low, other than setting an arbitrary limit? During acceleration the manifold vacuum and vehicle fuel mileage can be seen to drop precipitously, but how much is too much? Additional devices have been developed to guide vehicle operators to operate the vehicle in more fuel efficient ways, such as upshift indicators or devices to signal the operator that operation exceeds an arbitrary value. Such devices often become mere annoyances.
The above devices ignore two parameters that are of equal or more importance to the operator; namely, the time to reach a destination and the cost of fuel in currency such as dollars. Most individuals consider their time to be important or of value, which is why they use a vehicle instead of other modes of transportation. Most vehicle operators therefore simply ignore the fuel mileage display and travel at or near or above the maximum safe or legal speed.
During the 1980s and early 1990s, fuel was abundant and prices were relatively low yet the 55 mph speed limit remained and was heavily enforced. As it turns out, however, driving 55 mph saves only a few dollars of fuel per hour of increased travel time. High rates of acceleration reduce travel time, but overall fuel consumption may not be dependent on the rate of acceleration. A few seconds of coasting from slower speeds yields worthwhile savings, but eventually the savings become insignificant at slow speeds. However, even though the savings in fuel and increased time may be small for each event, over many such events of a single trip or a lifetime of driving and the entire vehicle population the savings could become significant and worthwhile doing for most operators. Consequently, an improved way to convey this information to operators of powered vehicles would be of considerable value.